I'm not entirely sure what you mean here... But a while back I found my eyedropper didn't seem to do anything, and it was because it was changing the background colour, not the foreground colour that you paint with. I'll save you the google search and paste in the solution I found:

"There's a menu on the right in Photoshop CS, it's labeled "Color" (F6 brings it up) it has two boxes of color that show the current foreground and background colors. One will have a black outline around the color box and the other will have a slightly lighter gray box around it. For some reason these outlines are almost indistinguishable from each other, thin, and hard to see... but they control which box is active. You want to click on the edge of the one in front (the foreground color) to change the current tool default to that box. "

It helped a bit I suppose, meanng it picks up some colour. But whenever I eyedrop a black, it just doesnt do anything. It seems when I choose a dark colour it goes lighter. How do I reset everything? I dont wanna reinstall because I dont have the software anymore installed.

if you want to color pick just select colorpick tool from tool pallete in tool pallete u will find paint bucket option with color pik tool. just select it & click on the object where u want to pick the color. all the best._________________(no spam)

you can also set the colour picker to pick the value of a single pixel or the area around the pixel to a set radius. get the eye-dropper and right click if you want to try this out.

Otherwise you are probably picking a colour from what you see and painting further down the layer stack under some adjustment layers... I think there is an option with the eye dropper to actually choose between all layers and just the one you are on... but I think it only comes in in CS4.